Vapor generator



Patented Feb. 6, 1945 VAPOR GENERATOR John Blizard, Garden City, N. Y., assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York Application November 3, 1942, Serial No. 464,328

12 Claims. (Cl. 122-473) This invention relates to vapor generators, and more particularly to steam generators having one or more separately fired steam generating furnaces and a separately fired superheater furnace.

The present application is a continuation-inpart of application Serial No. 374,027, flied January 11, 1941.

At times, it is desirable to operate steam generators of this character so as to supply saturated steam only. During such operation in prior steam generators of this character, although no steam flows through the superheater and the superheater furnace ordinarily is not fired, the superheater itself will absorb a certain amount of heat by contact with the hot gases that circulate from the steam generator furnace, or by radiation from the furnace, or both. The superheater tubes and headers ordinarily will reach a temperature approximately that of the gases that penetrate the superheater furnace from one or more steam generating furnaces, and while this rate of heating of the superheater is not great, the superheater sometimes is heated above a reasonable temperature and is damaged.

The present invention overcomes this undesirable heating of the superheater in vapor generators of the character mentioned, and provides a method of and means for, automatically reducing the temperature of the superheater to a reasonable level when saturated steam only is supplied by the generator, or when steam superheated but slightly is required. With the present invention, when saturated steam or steam superheated but slightly is supplied by the generator, the superheater burner or burners may be retained in operation at a minimum firing rate so that a demand for superheated steam may be met immediately and Without the delay which would be occasioned by lighting the burner, or the superheater burner or burners may .be shut off entirely without damage to the tubes in the superheater furnace by gases passing over the tubes, because at all time when the superheater is not operating to supply superheated steam, a slight amount of steam is caused to flow through the superheater from the source of saturated steam.

The invention will be understood from the following description when considered in connection with the accompanying drawings forming a part thereof and in which:

Fig. 1 is a more or less diagrammatic vertical the invention;

Fig. 2 is an enlarged vertical sectional view of a part of the apparatus shown in Fig. 1;

Fig. 3 is a transverse sectional view taken on the line 3--3 of Fig. 2, and

Fig. 4 is a view similar to Fig. 1 but of. another form of the invention.

Like characters of reference refer to the same or similar parts throughout the several views.

Referring to Figs. 1, 2 and 3 of the drawings, reference numeral In designates generally the setting of a steam generator having a steam generator furnace I I fired by burners I2, and a superheater furnace I3 fired by a burner I4. An upper steam and water drum I5 is connected to a lower drum I6 by a vertically inclined bank of steam generating tu-bes I1, and to a lower drum I8 .by a group or screen of steam generating tubes I9 which extend between the steam generator furnace II and the superheater furnace I3. In the superheater furnace, are groups of superheater tubes '20 and 2I which are connected at'their upper ends to an inlet header 22 and at their lower ends to an outlet header 23. The upper drum I 5 is provided with a saturated steam nozzle 24 having an orifice plate 25 suitably secured to the inlet end of the nozzle by studs 23 or the like. The nozzle 24 is connected to a saturated steam line 21 which is controlled by a valve 23. The drum I5 also-has a main nozzle 29 which is connected to the inlet header 22 of the superheater by a steam pipe 30. A conduit 3I, of relatively small diameter. extends from the superheater outlet header 23 to a point 32 in the nozzle 24 ahead of the valve 28 with respect to the direction of flow of the saturated steam through the steam line 2'7.

The steam generator illustrated, is provided with a single outlet flue 33 for the gases from both fumaces. The arrangement is such that the gases from the superheater furnace, after flowing in heat exchange relationship with the superheater tubes 20 and 2|, pass over the tubes I9 and enter the steam generator furnace II, and

the gases from both furnaces pass over the bank of tubes I1 and enter the flue 33. Heat recovery apparatus, such as an economizer 34, is disposed in the flue 33. superheated steam is withdrawn from the superheater outlet header 23 through a main steam line 35 which is controlled by a valve 36. If desired, the conduit 3| may be connected to the main steam line 35 between the superheater outlet header 23 and the valve 36, instead of to the header as shown.

Normally, the generator will be operated to produce superheated steam, in which event the burners l2 in the steam generating furnace and the burners M in the superheater furnace will be operated and in the form of the invention shown in Fig. l, the valve 28 will be closed and the valve 36 will be open. A major portion of thesteam generated will flow through the nozzle 29 and steam pipe 38, to and through the superheater to the outlet header 23 from which it is conducted through the mainsteam line 3-5 and open valve 36 to apparatus requiring superheated steam. Only a small portion of the steam will flow through the orifice in. the orifice plate 25 into the nozzle 24 and, since the control valve 28 controlling the saturated steam line 21 is closed when superheated steam only is required, steam in the nozzle 24 will flow through the conduit 3| into the outlet header 23 of the superheater and become mixed with the superheated steam. .The flow of steam from the superheater through the main steam line 35 is great enough to cause th pressure of the steam in the outlet header 23 and line 35 to be lower than at the point 32 so that fiow through the by-pass 3| is assured. When only saturated steam or steam but slightly superheated is required, valve 28in the saturated steam line 21 is opened, valve 36 in the superheated heater against overheating by the gases which may fiow from the steam generating furnace into contact with the superheater tubes, or from heat radiated from the steam generating furnace, or both, and also against overheating by the gases produced inthe superheater furnace when the burners It are operated at a minimum, a small amount of saturated steam is caused to flow from the drum l5 through the nozzle 23, line 30, and through the'superheater to the outlet header 23, and thence through conduit 3| into the nozzle 24, where it will mix with the saturated steam being withdrawn from the steam line 21. The fiow of steam in the by-pass conduit 3 I, when the genera tor is operated to supply saturated steam only, is in a direction opposite to the direction of fiow of steam therein when the generator is operated to produce superheated steam. With this ar rangement, there is a constant flow of steam through the superheater tubes 28 and 2| when the generator is operated to produce saturated steam only, and this constant flow of steam is assured,

since most of the steam generated will be withdrawn from the drum l5 through the orifice in the plat 25 which will result in a pressure drop and will cause the pressure in the nozzle 24 near the point 32 where conduit 3| is connected with the nozzle, to be less than the pressure in the superheater outlet header 23, so that steam will flow from the drum to and through the super.- heater into the outlet header 23, and upwardly through the conduit 3| to the point 32 in the nozzle 24. It will be understood that the extent of the pressure drop from the drum to the downstream side of the orifice 25 may be varied as desired by regulation of the size of the opening in the orifice.

In the event it is undesirable to dilute the superheated steam with saturated steam, an arrangement such as shown in Fig. 4 may be utilized. Referring to Fig. 4, the conduit 3| has fiow controlling means comprising a check valve '31 which is constructed and arranged to permit flow through the conduit from the superheater to the steam nozzle 24, but automatically to prevent flow therethrough in the opposite direction, and a manually operated valve 88. The valves 31 and 38 prevent the flow of steam through the conduit 3| toward the superheater, when superheated steam is produced, regardless of changes in the operating conditions of the generator. For example, when the superheater is operated to supply superheated steam, there is generally a drop in pressure through the superheater of such a magnitude that saturated steam would be induced to fiow through conduit 3| from the saturated steam nozzle to the superheater outlet header. When this condition arises, the check valve 31 will close automatically, or the valve 38 may be closed manually, thus preventing the passage of saturated steam through conduit 3| to the outlet header of the superheater. Ordinarily, the check valve 31 or th manually operated valve 38 will i be sufiicient to control the conduit 3|, but both valves may be utilized, if desired.

Since a constant .fiow of steam through the superheater is at all times automatically maintained in the apparatus disclosed, it is possible to fire the burners in the superheater furnac at a minimum rate when there is no demand for superheated steam and-the generator is being operated to supply only saturated steam or steam superheated but slightly, without damage to the tubes of the superheater. Maintaining the superheater burners in operative condition, makes it possible to supply superheated steam very promptly, since a small amount of superheated steam is already flowing through the superheater and a burner is already ignited, thereby saving time required to ignite the burners and start the flow of superheated steam through the superheater.

Although preferred embodiments of the invention have been disclosed, it will be understood that the invention is applicable to any vapor generator having one or more Vapor generating furnaces and a separately fired superheater so disposed that it may be overheated by gases of rad aand that the invention is not to be limitedexcepting by the scope of the appended claims.

What is claimed is:

1. A vapor generator comprising a setting, vapor generating tubes in the setting, a. furnace, means for firing the furnace, saturated vapor conducting means through which saturated vapor is withdrawn from the generator and is conducted to a point of use, a superheater outside the furnace, separate means for firing the superheater, conduit means connecting the superheater and the generator through which saturated vapor flows to the superheater, an outlet conduit through which vapor is withdrawn from the superheater and is conducted to another point of use, a connecting conduit for conducting vapor which fiows through the superheater to the saturated vapor conducting means, control means for controlling the fiow of saturated vapor through the saturated vapor conducting means positioned beyond the point of connection of the connecting conduit with the saturated vapor conducting means in the direction of flow of the vapor control means for controlling the flow of superheated vapor from the superheater positioned beyond the end of the connecting conduit which first receives superheated vapor in the direction 01' fiow of vapor from the superheater, and a pressure drop device disposed in the path of flow of saturated vapor between the vapor generating tubes and the point at which the connecting conduit connects with the saturated vapor conducting means.

2. LA vapor generator comprising a setting,-vapor generating tubes in the setting, a furnace, means for firing the furnace, saturated vapor conducting means through which saturated vapor is withdrawn from the generator and is conducted to a point of use, a. superheater outside the furnace, separate means for firing the superheater, uncontrolled conduit means connecting the superheater and the generator and through which saturated vapor flows to the superheater at all times during the operation of the vapor generator, an outlet conduit through which vapor is withdrawn from the superheater and is conducted to another point of use, a connecting conduit for conducting vapor which flows through the superheater to the saturated vapor conducting means, control means for controlling the flow of saturated vapor through the saturated vapor conducting means positioned beyond the point of connection of the connecting conduit with the saturated vapor conducting means in the direction of flow of the vapor, control means for controlling the flow of superheated vapor from the superheater positioned beyond the end of the connecting conduit which first receives superheated vapor in the direction of flow of vapor from the superheater, and a pressure drop device disposed in the path of fiow of saturated vapor between the vapor generating tubes and the point at which the connecting conduit connects with the saturated vapor conducting means.

3. A vapor generator comprising a setting, a

vapor and liquid drum in the setting, vapor gen- 1 erating tubes connected with said drum, a furnace, means for firing the furnace, means for withdrawing vapor from the drum and through which vapor is conducted to a point of use, a

superheater in the setting outside said furnace,

separate means for firing the superheater, conduit means connecting the drum and the superheater and through which vapor flows from the drum to the superheater at all times during operation of the vapor generator, an outlet conduit through which vapor is withdrawn from the superheater and is conducted to another point of use, a connecting conduit for conducting vapor which flows through the superheater to the means for withdrawing vapor from the drum, control means for controlling the flow of vapor from the drum through said means for withdrawing vapor from the drum positioned beyond the point of connection of the connecting conduit with the vapor withdrawing means in the direction of flow of the vapor, control means for controlling the flow of superheated vapor from the superheater positioned beyond the end of the connecting conduit which first receives superheated vapor in the direction of flow of vapor from the superheater, and a pressure drop device associated with said means for withdrawing vapor from the drum and disposed between the drum and the point of connecticn of the connecting conduit to the means for withdrawing vapor from the drum.

4. A vapor generator comprising a setting, a vapor. and liquid drum in the setting, vapor generating tubes connected with said drum, a furnace, means for firing the furnace, a conduit for withdrawing vapor from the drum and through which vapor is conducted to a point of use, a

superheater in the setting outside the furnace, said superheater having an inlet header and an outlet header, separate means for firingthe super heater, a conduit extending betweenthe drum and the inlet header of the superheater and through which vapor flows from the drum to the superheater at all times during the operation of the vapor generator, an outlet conduit connected flow of the vapor, control means associated with v the superheater outlet conduit to control the flow of vapor therethrough disposed beyond the point of connection of the connecting conduit with the superheater outlet header in the direction of flow of vapor from the superheater, and a pressure drop device associated with the conduit for withdrawing vapor from the drum and positioned between the drum and the point of connection of the connecting conduit to the conduit for withdrawing vapor from the drum.

5. A vapor generator comprising a setting, a vapor and liquid drum in the setting, a bank of vapor generating tubes in the setting and connected to said drum, other vapor generating tubes connected to said drum and spaced from said bank of tubes, a furnace between said bank of tubes and said other tubes, means for firing the furnace, saturated vapor conducting means through which saturated vapor is withdrawn from the generator and is conducted to a point of use, a superheater outside the furnace, separate means for firing the superheater, conduit means connecting the superheater and the drum and through which saturated vapor flows to the superheater at all times during the operation of the vapor generator, an outlet conduit through which vapor is withdrawn from the superheater and is conducted to another point oi use, a connecting conduit for conducting vapor which flows through the superheater to the saturated vapor conducting means, control means for controlling the flow of saturated vapor through the saturated vapor conducting means positioned beyond the point of connection of the connecting conduit with the saturated vapor conducting means in the direction of flow of the vapor, control means for controlling the flow of superheated vapor from the superheater positioned beyond the end of the connecting conduit which first receives superheated vapor in the direction of flow of vapor from the superheater, and a pressure drop device disposed in the path of flow of saturated vapor between the drum and the point at which the connecting conduit connects with the saturated vapor conducting means.

6. A vapor generator comprising a setting, a

vapor and liquid drum in the setting, a bank of through which saturated vapor is withdrawn from the generator and is conducted to a point of use,

a superheater outside the furnace, separate means for firing the superheater, conduit means connecting the superheaterand the drum and through which saturated vapor flows to the superheater at all times during the operation of the vapor generator, an outlet conduit through which vapor is withdrawn from the superheater and is conducted to another point of use, a connecting conduit for conducting-vapor which flows through the superheater to the saturated vapor conducting means, control means for controlling the fiow of saturated vapor through the saturated vapor conducting means positioned beyond the point of connection of the connecting conduit with the saturated vapor conducting means in the direction of flow of the vapor, control means for controlling the flow of superheated vapor from the superheater positioned beyond the end of the connecting conduit which first receives superheated vapor in the direction of flow of vapor from the superheater, and an orifice associated with said saturated vapor conducting means in the path of vapor flowing from the drum and positioned between the drum and the point at which the connecting conduit connects with the saturated vapor conducting means.

7. A vapor generator comprising a setting, two spaced groups of fuel burners in the setting, each group comprising at least one burner, a gas outlet for the setting at a point remote from said burners, a bank of vapor generating tubes disposed in the path of the gases produced by one group of burners in flowing to the flue,,another bank of vapor generating tubes and superheater tubes disposed intermediate said burner groups and in the path of the gases produced by the other group of burners in flowing to the flue, the arrangement being such that the gases produced by said other group of burners fiow over said first mentioned tube bank prior to entering the flue, saturated vapor conducting means through which saturated vapor is withdrawn from the generator and is conducted to a, point of use, conduit means adapted to receive saturated vapor from the vapor generating tubes and to pass it to the superheater at all times during the operation of the vapor generator, an outlet conduit through which vapor is withdrawn from the superheater and is conducted to another point of use, a connecting conduit for conducting vapor which flows through the superheater to the saturated vapor conducting means, control means for controlling the flow of saturated vapor through the saturated vapor conducting mean positioned beyond the point of connection of the connecting conduit with the saturated vapor conducting means in the direction of flow of the vapor, control means for controlling the flow of superheated vapor from the superheater positioned beyond the end of the connecting conduit which first receives superheated vapor in the direction of flow of vapor from the superheater, and a pressure drop device disposed in the path of fiow of saturated vapor between the vapor generating tubes and the point at which the connecting conduit connects with the saturated vapor conducting means.

8. A vapor generator comprising a setting, a vapor and liquid drum in the upper part of the setting, spaced liquid drums in the lower part of the setting, a bank of boiler tubes connecting the vapor and liquid drum and each of the lower drums. said tube banks defining a furnace chamber between them at least in part, at least one fuel burner for firing th furnace, a superheater disposed outside of said furnace and separated therefrom by tubes of one of said tube banks and having tubes thereof disposed adjacent tubes of said one bank, at least one fuel burner for firing the superheater, and a-flue connecting with the setting and having a single inlet into which fiow all the products of combustion produced by said burners, said flue inlet being located so that the products of combustion produced by the at least one burner for firing the superheater flow over tubes of the superheater and each of said tube banks prior to entering the flue, a conduit for withdrawing vapor from the drum and through which vapor is conducted to a point of use, a superheater in the setting-outside the furnace, said superheater having an inlet header and an outlet header, means for firing the superheater, a conduit extending between the drum and the inlet header of the superheater and through which vapor flows from the drum to the superheater at all times during the operation of the vapor generator, an outlet conduit connected to the superheater outlet and through which vapor is withdrawn from the superheater and is conducted to another point of use, a connecting conduit extending between the superheater outlet header and the conduit for withdrawing vapor from the drum, control means associated with the conduit for withdrawing vapor from the drum for controlling the flow of vapor therethrough and disposed beyond the point-of connection of the connecting conduit with the conduit for withdrawing vapor from the drum in the direction of flow of the vapor, control means associated with th superheater outlet conduit to control the fiow of vapor therethrough and disposed beyond the point of connection of the connecting conduit with the superheater outlet header in the direction of flow of vapor from the superheater, and a pressure drop device associated with the conduit for withdrawing vapor from the drum and positioned between the drum and the point of connection of the connecting conduit to the conduit for withdrawing vapor from the drum.

9. A vapor generator comprising a setting, vapor generating tubes in the setting, a furnace, means for firing the furnace, saturated vapor conducting means through which saturated vapor is withdrawn from the generator and is conducted to a point of use, a superheater outside the furnace, separate means for firing the superheater, conduit means connecting the superheater and the generator and through which saturated Va'por flows to the superheater at all times during the operation of the vapor generator, an outlet conduit through which vapor is withdrawn from the superheater and is conducted to another point of use, a connecting conduit for conducting vapor which flows through the superheater to the saturated vapor conducting means, flow controlling means in the connecting conduit permitt ng vapor to flow only from the superheater, control means for controlling the flow of saturated vapor through the saturated vapor conducting means positioned beyond the point of connection of the connecting conduit with the saturated vapor conducting means in the direction of flow of the vapor, flow control means for controlling the flow of superheated vapor from the superheater positioned beyond the end of the connecting conduit which first receives superheated vapor in the direction of flow of vapor from the superheater, and a pressure drop device disposed in the path of flow of saturated vapor between the vapor generating tubes and the point at which the connecting conduit connects with the saturated vapor conducting means.

10. A vapor generator comprising a setting, vapor generating tubes in the setting, a furnace, means for firing the furnace, saturated vapor conducting means through which saturated vapor is withdrawn from the generator and is conducted to a point of use, a superheater outside the furnace, separate means for firing the superheater, conduit means connecting the superheater and the generator and through which saturated vapor flows to the superheater at all times during the operation of the vapor generator, an outlet conduit through which vapor is withdrawn from the superheater and is conducted to another point of use, a connecting conduit for conducting vapor which flows through the superheater to the saturated vapor conducting means, flow controlling means in the connecting conduit, control means for controlling the flow of saturated vapor through the saturated vapor conducting means positioned beyond the point of connection of the connecting conduit with the saturated vapor conducting means in the direction of flow of the vapor, flow control means for controlling the flow of superheated vapor from the superheater positioned bound the end of the connecting conduit which first receives superheated vapor in the direction of flow of vapor from the superheater, and a pressure drop device disposed in the path of flow of saturated vapor between the vapor generating tubes and the point at which the connecting conduit connects with the saturated vapor conducting means.

11. The method of generating vapor in a generator having a separately fired superheater, which includes passing saturated vapor from a saturated vapor generating zone through a zone of reduced pressure to a point of use, controlling the amount of saturated vapor passed from the saturated vapor generating zone, passing superheated vapor to another point of use, flowing saturated vapor from the saturated vapor generat-.

ing zone through the superheater at all times during the generation of vapor, and flowing the vapor passed through the superheater into the zone of reduced pressure when the generator is operated to produce saturated vapor only or only slightly superheated vapor.

12. The method of generating vapor in a generator having a 'separately fired superheater, which includes passing saturated vapor from a saturated vapor generating zone through a zone of reduced pressure to a point of use, controllin the amount of saturated vapor passed from the saturated vapor generating zone, passing superheated vapor to another point of use, flowing saturated vapor in an uncontrolled flow path from the saturated vapor generating zone through the superheater, and flowing the vapor passed 

